in order to play pop'n music on PCSX2 with an official controller, the pad plugin must allow on the d-pad left and right to be pressed simultaneously
the limitation of not pressing left+right simultaneously is just a physical limitation of the standard PS pad, and not a constraint of the console itself.

the board in a P'NM controller is just a standard PS pad board, with the left+right+down soldered together.
when these directions are pressed down the game recognizes the controller not as a standard one but as a P'NM one.

therefore i think that a pad plugin should allow these 2 directions to be pressed simultaneously.
note that it also needs to record that state since the launch of the game, as it seems that it needs the effective press of a button to record that.

the plugins i tried act as if there were 2 states : "just pressed" and "already pressed" and only trigger the push of a button on a "just pressed" event, so the plugin must be able to detect the "already pressed" configuration as the game starts.

i hope my description is clear (maybe needs to be in "bug report" ?), and thanks a lot for helping all pop'n music players !